Interferon-γ receptor-1 gene promoter polymorphisms (G-611A; T-56C) and susceptibility to tuberculosis

We analysed frequencies of two single-nucleotide polymorphisms (SNP) in the interferon-gamma (IFN-gamma) receptor-1 (IFNGR1) gene promoter (G-611A, T-56C) in tuberculosis patients (n = 244) and compared them with controls (n = 521). These frequencies were not significantly different, whether analysed independently or as haplotypes. Because these SNP affect transcription, the results suggest that the expression of the IFNGR1 gene does not confer susceptibility to disease in patients from Croatia. Further analysis revealed a significant association between the protective (CA)(n) polymorphism (22 repeats, 192 FA(1)), located in the fifth intron of the IFNGR1 gene (+16682), and GT promoter haplotype (-611; -56) that showed the strongest expression capacity. In addition to this cis relationship, the (CA)(22) allele was correlated in trans with an IFN-gamma SNP (IFNG G + 2109A), which might affect the transcription of the IFNG gene. These results suggest that a particular combination of IFNG and IFNGR1 SNP might offer a better protection against tuberculosis in this population.